Last week, as Parisians were choked by the city’s worst, Eiffel Tower-obscuring smog since 1997, they were left to ask the same, depressing question: How does this compare with Beijing?

As it happens, not well. For a few days at least, the air quality in Paris was much worse than in Beijing. (This was partially due to an unusual clean spell in Beijing.)

Paris responded by imposing an alternating-day driving ban, starting Monday with even-numbered plates and continuing on Tuesday with odd-numbered ones. That seemed to do the trick. On Monday, after one day of restrictions, the smog lifted and so did the ban. “Bravo, and thank you,” wrote Philippe Martin, France’s ecology minister, in a message to the city’s car owners.

He shouldn’t get too cocky.

As a short-term, politically expedient solution, driving bans can be highly effective. But long term, study after study shows that driving bans are not only ineffective but also possibly counterproductive as drivers figure out ways to circumvent the regulations, sometimes by purchasing cars that can be used on restricted days (a car for Monday, a car for Tuesday), switching commutes ― and pollution ― to non-restricted hours or simply choosing longer routes that avoid restricted roads while requiring more fuel.

Consider, for example, Beijing’s experience both before and after the 2008 Olympics. In advance of the games, Beijing promised to clean up the city’s air. The government shut down polluting industries around the capital and forced 300,000 vehicles off the roads during the games. It also required new cars to meet European emission standards and imposed an alternating-day car ban much like the one in Paris, resulting in a daily reduction of two million on-road vehicles. The results were spectacular: Compared with 2007, emissions of black carbon by diesel vehicles ― the source of much of the pollution in Beijing and Paris ― declined 33 percent, according to a Cornell University study.

In October 2008, the driving restrictions were loosened to a once-per-week prohibition (based on the last digit of license plate numbers), which remains in effect. Predictably, Beijing gave back air-quality gains (not all or even most givebacks relate to cars; restrictions on industry in and around Beijing also were given back). A 2011 study by the U.S. National Bureau of Economic Research found that 60 percent of Beijing’s substantial Olympics-related gains in pollution control in 2008 had evaporated within a year. As for car-specific pollution, data collected from an unpublished study at the University of California at Davis has failed to find any evidence that a post-Olympics driving ban reduced pollutants.

In fact, the most tangible outcome of that and other post-Olympics driving bans is that they gave Beijingers a long-term incentive to circumvent them ― an incentive that didn’t exist with the Olympics ban. According to a September 2013 study by Environment for Development, a project of the Swedish International Development Cooperation, 47.8 percent of Beijing’s regulated car owners now violate the restrictions and drive illegally on a regular basis. In Beijing, where circumventing driving bans (including restrictions on obtaining a license plate) has literally become an industry, this comes as no surprise.

Purchasing additional cars to get around bans isn’t unknown; counterfeiting and renting license plates are common. Indeed, since the end of the Olympics, according to Environment for Development, Beijing’s used-car sales doubled, and in 2010 traffic-congestion measurements almost equaled those in 2007.

Why should Paris care? There’s no telling whether Monday’s one-day driving ban was decisive in cleaning up the city’s air. But assuming it was, part of the reason is that the city’s drivers were caught off-guard and simply didn’t have a chance to figure out ways around the policy. As a long-term solution ― and sooner or later Paris will need one ― a driving ban, even one combined with free public transport, as Paris offered over the weekend, won’t do much more than create committed lawbreakers. The experiences of Beijing and other cities around the world have proven that.

The long-term solution to Paris’s woes will require politically hard choices, starting with a long delayed elimination of subsidized, highly polluting (compared with gasoline) diesel fuel, which France uses far more than most developed countries. It won’t be easy; diesel has strong industry and political support in France. But if the city hopes to avoid comparisons with Beijing, it would be well-advised to avoid repeating Beijing’s gimmicky mistakes.

By Adam Minter

Adam Minter is a regular contributor to Bloomberg View based in Shanghai and the author of “Junkyard Planet,” a book on the global recycling industry. ― Ed.

(Bloomberg)